Build with ParaView in CI on Ubuntu.

[mmuetzel]

This enables ParaView in the CI on Ubuntu.

The ubuntu-latest label is still pointing to Ubuntu 22.04. Unfortunately, there is a package conflict that prevents installing ParaView on the runner:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 python3-paraview : Conflicts: python3-vtk9 but 9.1.0+really9.1.0+dfsg2-3build1 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
Error: Process completed with exit code 100.

That package conflict is resolved in Ubuntu 24.04. Runner images with that version of Ubuntu are already hosted as a beta by GitHub: actions/runner-images#9848

For the time being, pin the runner image to ubuntu-24.04. That part of the change should be reverted some time after the ubuntu-latest label starts pointing to ubuntu-24.04 (so the CI won't be stuck at an eventually old version of Ubuntu).

[raback]

I wonder whether any paraview library is needed here. To my recollection "WITH_PARAVIEW" only means that you can launch paraview directly from ElmerGUI (menu & button) but this is just a system command. To be honest, the "WITH_PARAVIEW" could be there always since almost everybody uses that.

[mmuetzel]

Good point. I was confused by the following:

elmerfem/ElmerGUI/Application/src/mainwindow.cpp

Lines 7275 to 7279 in a6ad3b1

	#ifdef EG_PARAVIEW
	"<P>This version of ElmerGUI has been linked "
	"against ParaView visualization software.<BR>"
	"<A HREF='https://www.paraview.org/'>https://www.paraview.org</A></P>"
	#endif

But afaict, ElmerGUI isn't actually linked against ParaView. It just starts it as a separate process.

I force pushed a change that enables ParaView everywhere but doesn't install the program itself. IIUC, it isn't actually needed that ParaView is installed to be able to build the respective parts of the code.